Optimization dyestuff adsorption on cationic surfactant-modified clinoptilolite using box-behnken experimental design

The effective use of clinoptilolite (CPT) as an adsorbent for removing anionic dyes is hindered by a high negative charge density on its surface. This study aimed to enhance the CPT surface's ability to remove Reactive Blue 171 (RB171) dyestuff from water. This was achieved by modifying the CPT surface using hydrochloric acid, sodium chloride, and hexadecyltrimethylammonium bromide (HDTMA). The maximum adsorption capacity was attained through modification using CPT@HDTMA. The elimination of RB171 was examined utilizing CPT and CPT@HDTMA, and an optimization process was conducted using the Box-Behnken experimental design (BBD). The highest adsorption efficiency for both adsorbents was observed at pH 1,0 Kinetic studies showed that both adsorbents followed the pseudo-second-order kinetic model, with CPT@HDTMA exhibiting a faster adsorption process and reaching equilibrium faster with increasing temperature. Equilibrium data revealed that the adsorption of RB171 on CPT and CPT@HDTMA fit the Freundlich and Langmuir isotherm models, respectively. Thermodynamic analysis showed that CPT was more effective at low temperatures, and CPT@HDTMA was more effective at high temperatures according to ΔG° values. Experiments carried out in a continuous system revealed that CPT@HDTMA was more effective than CPT. BBD optimization experiments with four parameters and five centers for RB171 adsorption on CPT@HDTMA were carried out. The optimum conditions were pH 1,02 adsorbent amount 11,08 mg, initial RB171 concentration 191,8 mg/L, and contact time 100,4 minutes. Under these conditions, the maximum adsorption capacity of CPT@HDTMA was determined as 202,34 mg/g.